1. การสื่อสารข้อมูลและเครือข่าย คอมพิวเตอร์ Data Communication and Networks บทที่ 2 พื้นฐานข้อมูลและ สัญญาณ อาจารย์ผู้สอน : ดร. วีรพันธุ์ ศิริฤทธิ์ E-Mail : siririth @ gmail.com

2. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Analog Transmission

3. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 5.1 Modulation of Digital Data Digital-to-Analog Conversion Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) Quadrature Amplitude Modulation Bit/Baud Comparison

4. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.1 Digital-to-analog modulation

5. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.2 Types of digital-to-analog modulation

6. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Bit rate is the number of bits per second. Baud rate is the number of signal units per second. Baud rate is less than or equal to the bit rate. Note:

7. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Example 1 An analog signal carries 4 bits in each signal unit. If 1000 signal units are sent per second, find the baud rate and the bit rate Solution Baud rate = 1000 bauds per second (baud/s) Bit rate = 1000 x 4 = 4000 bps

8. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Example 2 The bit rate of a signal is 3000. If each signal unit carries 6 bits, what is the baud rate? Solution Baud rate = 3000 / 6 = 500 baud/s

9. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.3 ASK

10. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.6 FSK

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.8 PSK

12. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Quadrature amplitude modulation is a combination of ASK and PSK so that a maximum contrast between each signal unit (bit, dibit, tribit, and so on) is achieved. Note:

13. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.17 Bit and baud

14. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 5.2 Telephone Modems Modem Standards

15. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 A telephone line has a bandwidth of almost 2400 Hz for data transmission. Note:

16. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.18 Telephone line bandwidth

17. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Modem stands for modulator/demodulator. Note:

18. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.19 Modulation/demodulation

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.22 Traditional modems

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.23 56K modems

21. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 5.3 Modulation of Analog Signals Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM)

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.24 Analog-to-analog modulation

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.25 Types of analog-to-analog modulation

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.26 Amplitude modulation

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 5.29 Frequency modulation